P =AD,
P = Monthly payment
A = Cost of the car
D = [R/12]/[1-(1+R/12)^-12n], where R = Annual interest = 5.4% = 0.054, n = Number years = 5
Therefore,
D = [0.054/12]/[1-(1+0.054/12)^-12*5] = 0.019055
And,
P = 6,900*0.019055 = $131.48
Monthly payment will be $131.48.