Consider an economy in which the price level is equal to one unit and the goods and money market are described by the following equations:

• consumption C = 400 + 0.2(Y-T)
• investment I = 80 + 0.5Y -10r
• G=T= 100
• Money Demand Md = 100 + Y - 50r
• Money supply Ms = 100

Find the equilibrium r.

• A.8.0
• B.17.8
• C.20.2
• D.22.4