please help!

Biochemical Corporation requires $$650,000$ in financing over the next three years. The firm can borrow the funds for three years at

$12\mathrm{.}60$ percent interest per year. The CEO decides to do a forecast and predicts that if she utilizes short$-$term financing instead, she will

pay $9\mathrm{.}25$ percent interest in the first year, $13\mathrm{.}50$ percent interest in the second year, and $10\mathrm{.}50$ percent interest in the third year.

Assume interest is paid in full at the end of each year.

a$.$ Determine the total interest cost under each plan.

b$.$ Which plan is less costly$?$

Short$-$term variable$-$rate plan

Long$-$term fixed$-$rate plan