Asonar system measures distance by determining the takes for sound waves to bounce off a surface.

Time

Explanation:

The sonar is constantly sending signals into the space surrounding him, then he measures the waves that come back by bouncing in surfaces and it calculates the distance that it took those waves to come back to see how far away the surface located is.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.