Using the MARIE computer assembly language, write a program that computes the following expression: z $=($a $*$ b$)+($c $*$ d$).$ The computer will read in the input values a$,$ b$,$ c$,$ and d from the keyboard, the final result $($z$)$ has to be displayed. In addition, every time an input value is read in$,$ it must be validated by checking that the input is a positive number. If it is positive display the number on the screen; otherwise display zero and end the program. Remember that the MARIE instruction set does not have an instruction to execute multiplication.