ished your project and it is ready for grading Having finished the work on Casey's computer, you attempt to save the changes and find that this is function is protected by a password. You click the "hint" option and are given the following: What exact value of r satisfies e21 - 4et - 21 = 0? If there is no solution, enter NA. Enclose arguments of functions in parentheses and include a multiplication sign between terms. For example, c * log (h). What value do you enter