A man steps outside one winter day to go to work. His icy driveway is \(8.0 \mathrm{~m}\) long from top to mailbox, and it slopes downward at \(20^{\circ}\) from the horizontal. He sets his briefcase on the ice at the top while opening the garage, and the briefcase slides down the driveway. Ignore friction.

(a) What is its acceleration?

(b) How many seconds does it take to get halfway to the mailbox?

(c) How many seconds does it take to reach the mailbox?

(d) What is its speed at the instant it reaches the mailbox?