Walt, who is in the 35% tax bracket, sells taxable bonds (at no gain or loss) which yielded $900 of interest annually and purchases tax-exempt bonds yielding $600 of annual interest. What is the net cash effect of these transactions to Walt for the year?

a. Decreases by $300.

b. Increases by $915.

c. Decreases by $900.

d. Increases by $15.

e. None of the above.