Examine main.cpp to see how the function is used, then write the correct prototype. Complete the following file: df.h 1 #ifndef DF_H 2. #define DF_H 3 4 // Write your prototype here 5 6 7 #endif Submit Use the following file: main.cpp #include "df.h" #include #include using namespace std; int main() { string s; cin >> S; cap(s); // Capitalize s cout #include using namespace std; int main() { string s; cin >> S; // Print capitalized version of s cout