3. Implement a substring search and reverse function which searches a string for a given keyword. The function should return a pointer to the address of the last character of the substring within the original string, if it exists. Additionally, the substring should be modified so that it is reversed. If the substring is not found within the string, return NULL. If the substring is found and reversed, print the modified string. If no substring is found, print "Key not found!" Your program's input and output should match what is seen in the example run. You may only use stdio.h. Save your code as swap_and_reverse.c. Example Run Enter string: this is a test string. Enter key: test this is a tset string