What is the degree of this polynomial -2a^3b^2+5ab^5+7b^4+8

For this case we have the following polynomial:
 
 We observe that we have a polynomial of two varibles.
 Variables: a and b
 The degree of the polynomial is given by the highest sum of the exponents of the variables.
 We have then for the following term:
 
 The sum of the exponents is:
 
 Therefore, the polynomial is of degree 6.
 
 the polynomial is of degree 6.