$3\mathrm{.}5$ Lab $5$ Calculator $($UART Application$)$Lab Objectives To apply knowledge on the use of serial ports gained in lab $4$ to solve adesign problemProblemYour group needs to develop a simple calculator program. Unlike theprevious labs, this lab will be done in C to provide some insight into howhigher level languages operate on microprocessors. The calculator will usethe serial routines from lab $4$ to handle the data input and output interfacewith the user. All code for this program can only use base C instructions andthe functions developed in lab $4.$ Use of other libraries, for examplestring.h$,$ stdlib.h and stdio.h$,$ is prohibited in the solution of thisproblem.It can be useful to approach the problem it functionality tiers. Each tier isslightly more advanced than the previous one.For tier $1,$ the calculator needs to take in $2$ four$-$digit numbers separated bya plus sign and return the answer after an equals sign.Examples: User enters, Program returns$0001+0001=000020100+0020=001201234+5678=069129999+9999=19998$Notice that the user is always entering four digits, even for values less than$1000.$ Also, notice the result is always five digits. The four digit decimalvalues have a range of $0000$ to $9999,$ giving the range of the sum to be$0000$ to $19998.$For tier $2$ functionality is removing the need to enter the leading zeros.Examples:$1+1=00002100+20=00120$