$13-$ Trace the Q$12$ reverse polish expression to evaluate the value by the following algorithm.

$($Stepwise solution is needed$)(3$ marks$).$

The following algorithm evaluates RPN expressions

Step $1$:

Start at left and look at expression until you come to an operator

Step $2$:

Replace the two numbers to the left of the operator with the result of

performing the operator on the two numbers

Step $3$:

If the formula now consists of only one number that is the result; if not

continue to look for an operator and continue with step $2.$