Examine main.cpp to see how the function is used, then write the correct prototype. This is a little harder than the previous two exercises. Complete the following file: df.h 1 #ifndef DF_H 2 #define DF_H 3 4 // Write your prototype here #include 6 | 7 8 #endif Submit Use the following file: main.cpp #include "df.h" #include #include using namespace std; int main() { string s; cap(cin, s); // read into s; convert to caps cout