Math / Qunatitative Decision Making

I am taking a course that I need assistance with. I have no way of knowing if I am answering the questions right. Is anyone familiar or able to assist me with the class? I want to find someone now to start working on problems that are due next Saturday. I don't have the problems just yet. Explanations need to be shown while answering the quesiotns. 

The book is Quantitative Analysis for Management by Render, Stair, Hanna and Hale 12th ed. 2015.

The class covers:

quantitative analysis, probabitiy concepts and application, decision analysis, regression models, forecasting, inventory control models, linear programming models/graphical and compuer methods, linear programming applications, transportaiont/assignment/network models, integer programming/goal programming/nonlinear programming, project management, waiting lines and queuing theory models, simulation modelsing,markov analysis, statiscial quality control.

Here's a question from last week: A student taking Management Science  will receive one of the five possible grade for the course: A, B, C, D, or F. The disribution of grades over the past 2 yesar is as follows:

Grade              # of Students

A                         80

B                         75

C                        90

D                        30

F                         25

             total      300

If this past distribution is a good indicator of furture grades, what is the probabilty of a student receiving a C in the course?