Shown is part of a temperature control program with math instructions. Start and PB$\_$Set are normally open switch and push button respectively. The desired temperature is given by Local:$4$:I.Ch$0$Data and the measured temperature is given by Local:$4$:I.Ch$1$Data, they are both in normal decimal form and in range of $0$ to $1000C(\frac{?}{?}F),$ a$)$ Explain how the program works, b$)$ If the desired temperature is entered as $7500$ instead of $750$ accidently, which math instruction will cause an error? What type of error is it and how can it be detected? All numeric tags are of type INT $(16$ bit integer$).$

op

$0$

PB$\_$Set

$$ Local:$2$:I.Da

$=0$

$?{?}^{}$

Subtract

Source A Local:$4$:I.ChOData

Source B

$0$

$$

PB$\_$Set

Local:$2$:$1.$Data$\mathrm{.}1$

$1$

PB$\_$Set

Local:$2$:I.Data$\mathrm{.}1$

$2$

$3$

$4$

Light$\_$high

Light$\_$low

$\backslash$table$[[$Divide$,],[$Source A$,$Value$\_2],[$Source B$,0+$