求教：两个数的乘积再加一个数如何实现

    .model tiny
    .code
    main proc far
start:
    xor ax,ax
    push ds
    push ax

    mov ax,0ffffh        ;short int a = 0xffff;
    mov dx,4             ;short int b = 4;
    mul dx               ;int c = a * b;
    mov bx,4240          ;short int d = 4240;
    add ax,bx
    adc dx,0             ;c += d;

    ret
    main endp
    end start