Answer
The braking force on each front wheel is $~~1200~N$
Work Step by Step
In part (c), we found that the normal force on each front wheel is $~~F_N = 3100~N$
We can find the braking force on each front wheel:
$F = F_N~\mu_k$
$F = (3100~N)(0.40)$
$F = 1200~N$
The braking force on each front wheel is $~~1200~N$