$273 ,000 being the equal  installments for  all the three years
Explanation:
 I year interest  = $ 630,000 ×15÷100 = 94,500 

 II year interest = $420,000×15÷100 =  63,000 

 III year interest = $210 ,000×15÷100 =  31,500 

Total interest = 94,500+63,000+31,500 = 189.000

Installments payment with interest for each year is=
(630,000 + 189,000 = 819,000÷ 3 = 273,000)

   = $273 ,000 being the equal  installments for  all the three years