Guess the error and tell me the correct answer

Question

#include <stdio.h>

int main() {
float a[]={13.24,1.5,1.5,5.4,3.5};
float *j,*k;
j=a;
k=k+4;
j=j*2;
k=k/2;
printf ("\n %f %f",*j,*k);
return 0;
}

Answer 1

there are four arithmetic operators that can be used on pointers: ++, --, +, and -