Consider the amortization schedule below for the repayment of a personal loan of $$25,000.$ The interest rate is $8\%$ annual nominal rate. The repayments are made every quarter over the next $4$ years.

$\backslash$table$[[$Amortization Schedule$],[$uanter$,$Interest:,Principal Paymen,Ending Balance$],[0,,,25000\mathrm{.}00],[1,500\mathrm{.}00,1341\mathrm{.}25,23658\mathrm{.}75],[2,473\mathrm{.}18,1368\mathrm{.}08,22290\mathrm{.}68],[3,445\mathrm{.}8],1395\mathrm{.}44,20895\mathrm{.}24],[4,417\mathrm{.}90,1423\mathrm{.}35,19471\mathrm{.}89],[5,389\mathrm{.}44,1451\mathrm{.}81,18020\mathrm{.}08],[6,360,40,1480\mathrm{.}85,16539\mathrm{.}23],[7,330\mathrm{.}78,1510\mathrm{.}47,15028\mathrm{.}77],[8,300\mathrm{.}58,1540\mathrm{.}67,13488\mathrm{.}09],[9,269\mathrm{.}76,1571\mathrm{.}49,11916\mathrm{.}60],[10,238\mathrm{.}33,1602\mathrm{.}92,10313\mathrm{.}69],[$II$,206\mathrm{.}27,1634\mathrm{.}98,8678\mathrm{.}71],[12,173\mathrm{.}51,1607\mathrm{.}68,7011\mathrm{.}03],[13,140\mathrm{.}22,1701\mathrm{.}03,5310\mathrm{.}01],[14,106\mathrm{.}20,1735\mathrm{.}05,3574\mathrm{.}96],[15,71\mathrm{.}50,1769\mathrm{.}75,1805\mathrm{.}20],[16,36\mathrm{.}10,1805\mathrm{.}15,0\mathrm{.}06]]$

Answer the following questions:

a$.$ What is the quarterly rate of interest?

b$.$ After I year, what is the balance of principle amount lent to be repaid? $($Of the original $$25,000$ how much is left to be repaid?$)$

c$.$ After $3$ years, what is the balance of principle amount left to be repaid? $($Of the original $$25,000$ how much is left to be repaid?$)$