J Paid Her 2012 Taxes by Filing Quarterly Estimated Tax

J paid her 2012 taxes by filing quarterly estimated tax payments of $2,000 each.She requested an automatic extension of the filing due date in March, 2013, and in July filed her completed return showing total 2012 tax liability of $9,500.If she paid $8,400 in 2012 taxes, enclosed no money with Form 4868 in March, and enclosed $1,500 with Form 1040 in July, what interest or penalty does she not owe?

A) Failure-to-file penalty
B) Failure-to-pay penalty
C) Interest on balance due
D) Penalty on underpayment of estimated tax