I believe the answer would be 6.96 cm
B = 3h . . . . . . . .given by the problem statement
A = (1/2)bh . . . . formula for the area of a triangle
486 cm² = (1/2)*(3h)*h . . . substitute given information
(2/3)*486 cm² = h² . . . . . .multiply by 2/3
√324 cm = h . . . . . . . . . . . . . .take the square root
The height is 18 cm.
The base is 3*18 = 54 cm.
June is 30 days
30-12=18 days
July is 31 days
August is 30 days
Time=18+31+30=79 days
A=2,750×(1+0.035÷365)^(79)
A=2,770.91
Interest earned
I=A-p
I=2770.91-2750
I==20.91