Parker, a gold miner, was given an $$18000$ loan by an investor. The conditions were interest would accumulate at a rate of $1\mathrm{.}9\%,$ compounded quarterly, and payments of $$1500$ are to be made at the end of every $3$ month period.

a$)$ How long can Parker expect it to take to repay his investor?

b$)$ What will he pay in interest?