Write a function str_replace that takes three strings, str1, str2 and str3; and replaces the first occurence (if any) of str2 in str1 with str3, and returns the newly formed string. For example,...

Write a function str_replace that takes three strings, str1, str2 and str3; and replaces the first occurence (if any) of str2 in str1 with str3, and returns the newly formed string. For example, str_replace("Nuclear Energy Engineering", "Nuclear Energy", "Mechanical") returns "Mechanical Engineering"