To compute for distance from a to b:
Distance A = 4 miles, base of triangle formed between a and b
Distance B = 3 miles, height of triangle formed between a and b
Distance AB = (A^2 + B^2)^0.5 hypotenuse of triangle formed between a and b, or square root of (A^2 + B^2)
Distance AB = ((4)^2 + (3)^2)^0.5
Distance AB = (16 + 9)^0.5
Distance AB = (25)^0.5
Distance AB = 5 miles
To compute for distance from b to where bank employee got stuck
BC = distance from b to c
BC = 4 miles
Total distance driven by bank employee
= AB + 0.5(BC)
= 5 + 0.5(4)
= 5 + 2
= 7 miles, total distance driven by the bank employee