For the polynomial - 2m2n3 2m? n3 7n2 - 6m4 to be a binomial with a degree of 4 after it has been fully simplified, which must be the missing exponent on the m-term?

For polynomials having two or more variables, degree can be of a term or of the polynomial. The degree of a term is the sum of the exponents in a specific term while the degree of a polynomial is the highest value of all the degree of a term in the given polynomial. From the polynomial,

-2m2n3 + 2m? n3 + 7n2 - 6m4

The missing exponent should be 2 so that the first and the second term is zero and what remains has a degree of 4.