The Money Market Practice Test

Based on the money market shown, the Federal Reserve conducts an open-market purchase of government securities, increasing the nominal money supply from $MS_1$ to $MS_2$ (a vertical shift right). Holding liquidity preference (money demand) constant at $MD_1$, what happens to the equilibrium nominal interest rate?

Based on the money market shown, which change most directly explains the shift in money demand from $MD_1$ to $MD_2$ (rightward), given that the nominal money supply remains fixed at $MS_1$ (vertical)?