Why errors when calculating an arithmetic expression?

Question

Algorithms

Hello! Check that the expression f = (ab)*c/2+d must be calculated incorrectly if a, b, c, d are byte, a=15, b = 70, c=25, d=35 We must also display the result in as a binary and hexadecimal value.

.model small
.stack 256
.data
a db 15
b db 70
c db 25
d db 35
f dw 0
.code
main:
   xor ax, ax
   mov al, 15
    mov bl, b
   cbw
   movsx ax, bx
   sub ax, bx
   imul c
   
   mov dl, d
   cbw
   movsx ax, dx
   add dx, 2
   
   idiv dx
   exit:
   mov ax, 4c00h
   int 21h
end main