Convert activity3.c below to a multi-file c program with 3 files: activity3.c, mymath. h, and mymath. c. give the gcc command to build the new program. don’t forget the include guards! when you are done, copy each file to this document in the appropriate place.
/* activity 3 - create a header file */
#include
#define pi 3.14159
int square(int x) {
return x * x;
}int main() {
int radius;
double area;
printf("enter the radius: ");
scanf("%d", & radius);
area = pi * square(radius);
printf ("the area of a circle with radius %d is %.2f\n", radius, area);
return 0;
}

Write a program that uses a two-dimensional array to store the highest and lowest temperatures for each month of the year. the program should output the average high, average low, and the highest and lowest temper- atures for the year. your program must consist of the following functions: a. function getdata: this function reads and stores data in the two- dimensional array. b. function averagehigh: this function calculates and returns the average high temperature for the year. c. function averagelow: this function calculates and returns the aver- age low temperature for the year. d. function indexhightemp: this function returns the index of the highest high temperature in the array. e. function indexlowtemp: this function retur