diff -r 8bdc44963c0c -r 2151c77e1e24 progs/drumb_sol.scala
--- a/progs/drumb_sol.scala	Thu Nov 17 16:21:56 2016 +0000
+++ b/progs/drumb_sol.scala	Fri Nov 18 18:47:02 2016 +0000
@@ -42,7 +42,7 @@
 
 
 // test case
-val p = get_prices(List("FB"), 2012 to 2014)
+val p_fb = get_prices(List("FB"), 2012 to 2014)
 val p = get_prices(List("GOOG", "AAPL"), 2005 to 2012)
 
 
@@ -79,7 +79,7 @@
   val somes_length = somes.length
   if (somes_length == 0) balance
   else {
-    val portion: Double = (balance.toDouble) / somes_length
+    val portion: Double = balance.toDouble / somes_length.toDouble
     balance + (for (x <- somes) yield (x * portion)).sum.toLong
   }
 }
@@ -115,3 +115,30 @@
 println("Real data: " + investment(rstate_portfolio, 1978 to 2016, 100))
 println("Blue data: " + investment(blchip_portfolio, 1978 to 2016, 100))
 
+val p_fb = get_prices(List("FB"), 2011 to 2016)
+
+// prices 2011 - 2016
+//    
+List(List(None), List(None), List(Some(28.0)), 
+     List(Some(54.709999)), List(Some(78.449997)), 
+     List(Some(102.220001)))
+
+// deltas 2011 - 2016
+val d_fb = get_deltas(p_fb)
+
+List(List(None), List(None), List(Some(0.9539285357142858)), 
+     List(Some(0.4339242996513305)), List(Some(0.30299560113431234)))
+
+yearly_yield(d_fb, 100, 0)   //2011  => 100
+yearly_yield(d_fb, 100, 1)   //2012  => 100
+yearly_yield(d_fb, 100, 2)   //2013  => 195
+yearly_yield(d_fb, 195, 3)   //2014  => 279   
+yearly_yield(d_fb, 279, 4)   //2015  => 363
+
+investment(List("FB"), 2011 to 2012, 100)  // => 100
+investment(List("FB"), 2011 to 2013, 100)  // => 100
+investment(List("FB"), 2011 to 2014, 100)  // => 195
+investment(List("FB"), 2011 to 2015, 100)  // => 279
+investment(List("FB"), 2011 to 2016, 100)  // => 363
+
+