(1) If the water fee in the first quarter is X, then the electricity fee in the first quarter is 2x-40. Since the first quarter is RMB ***a, x+2x-40=a and x=(a+40)/3, the electricity charge in the first quarter is 2x-40 = 2 (a+40)/3.

The water fee in the second quarter is 1.25 times that in the first quarter, that is,1.25x =1.25 (a+40)/3, that is, (5a+200)/ 12 yuan.

In the second quarter, 75%(2x-40)=0.75(2a-40)/3, namely (a-20)/2 yuan.

(2) In the first quarter, the water fee is still set to X, with

(x+2x-40)-[ 1.25 x+0.75(2x-40)]= 4 10

The solution is x= 1680 yuan.