Let f(x,y) = e +6y- 7+x. Complete parts (a) and (b) below. (a) Find f(-3,1). Select the correct choice below and, if necessary, fill in the answer box to complete your choice. A. f(-3,1)= (Type an exact answer in simplified form.) B. f(-3,1) does not exist. (b) Select the correct domain of f(x,y). A. {(x,y)|x7, y > 0} B. {(x,y)|x7, y is any real number} C. {(x,y)|x is any real number, y>0} D. {(x,y)|x is any real number, y is any real number}