diff -r 251d0ed461fb -r 58ec6da75f6f task4/solution07/src/org/apidesign/apifest08/currency/ConversionRate.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/task4/solution07/src/org/apidesign/apifest08/currency/ConversionRate.java	Sat Oct 11 23:38:46 2008 +0200
@@ -0,0 +1,91 @@
+package org.apidesign.apifest08.currency;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+/**
+ * A rate of conversion from one currency to another.
+ * @author jdvorak
+ */
+public class ConversionRate {
+
+    private final MonetaryAmount srcUnitAmount;
+    private final MonetaryAmount tgtUnitAmount;
+    private final int tgtScale;
+    private final RoundingMode roundingMode;
+
+    /**
+     * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount.
+     * @param srcUnitAmount the amount of source currency
+     * @param tgtUnitAmount the corresponding amount of target currency
+     * @param tgtScale the scale of the target amounts
+     * @param roundingMode the rounding mode to use when producing the target amounts
+     */
+    public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount, final int targetScale, final RoundingMode roundingMode ) {
+        this.srcUnitAmount = srcUnitAmount;
+        this.tgtUnitAmount = tgtUnitAmount;
+        this.tgtScale = targetScale;
+        this.roundingMode = roundingMode;
+    }
+
+    /**
+     * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount, default number of fraction digits and the given rounding mode.
+     * @param srcUnitAmount the amount of source currency
+     * @param tgtUnitAmount the corresponding amount of target currency
+     * @param roundingMode the rounding mode to use
+     */
+    public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount, final RoundingMode roundingMode ) {
+        this( srcUnitAmount, tgtUnitAmount, tgtUnitAmount.getCurrency().getDefaultFractionDigits(), roundingMode );
+    }
+
+    /**
+     * A new conversion rate that gives tgtUnitAmount per every srcUnitAmount, default number of fraction digits and {@link RoundingMode#HALF_EVEN}.
+     * @param srcUnitAmount the amount of source currency
+     * @param tgtUnitAmount the corresponding amount of target currency
+     */
+    public ConversionRate( final MonetaryAmount srcUnitAmount, final MonetaryAmount tgtUnitAmount ) {
+        this( srcUnitAmount, tgtUnitAmount, RoundingMode.HALF_EVEN );
+    }
+
+    public RoundingMode getRoundingMode() {
+        return roundingMode;
+    }
+
+    public MonetaryAmount getSrcUnitAmount() {
+        return srcUnitAmount;
+    }
+
+    public int getTgtScale() {
+        return tgtScale;
+    }
+
+    public MonetaryAmount getTgtUnitAmount() {
+        return tgtUnitAmount;
+    }
+    
+    /**
+     * Multiplies the given amount with the given rate.
+     * @param srcAmount
+     * @return
+     */
+    public BigDecimal convert( final BigDecimal srcAmount ) {
+        return srcAmount
+            .multiply( tgtUnitAmount.getAmount() )
+            .divide( srcUnitAmount.getAmount(), tgtScale, roundingMode );
+    }
+    
+    /**
+     * Creates a monetary amount that corresponds to the given source amount multiplied by the rate.
+     * @param srcAmount the source amount
+     * @return the monetary amount in the target currency
+     * @throws IllegalArgumentException if the currency of srcAmount is not equal to the source currency of this rate
+     */
+    public MonetaryAmount convert( final MonetaryAmount srcAmount ) {
+        if ( srcUnitAmount.getCurrency().equals( srcAmount.getCurrency() ) ) {
+            return new MonetaryAmount( convert( srcAmount.getAmount() ), tgtUnitAmount.getCurrency() );
+        } else {
+            throw new IllegalArgumentException( "This rate converts from " + srcUnitAmount.getCurrency() + ", but a conversion from " + srcAmount.getCurrency() + " is attempted" );
+        }
+    }
+    
+}