Horton equation:

f = f_c + (f_o - f_c) e^-kt

f - f_c = (f_o - f_c) e^-kt

2.75 - 1.4 = (f_o - 1.4) e^-k

1.85 - 1.4 = (f_o - 1.4) e^-2k

1.35 = (f_o - 1.4) e^-k

0.45 = (f_o - 1.4) e^-2k

Dividing these two equations:

3.0 = e^k

k = ln (3.0) = 1.0986 hr^-1    ANSWER.

Solving for f_o:

f_o = 1.35 e^k + 1.4

f_o = (1.35 × 3.0) + 1.4 = 5.45 mm/hr    ANSWER.

f_c = 1.4 mm/hr    ANSWER.

Verification:

f = 1.4 + (5.45 - 1.4) e^-1.0986 = 2.75 mm/hr   OK

f = 1.4 + (5.45 - 1.4) e^{-2 × 1.0986} = 1.85 mm/hr   OK