when user press ,the program calculates the summation of the four grades (Grade1+Grade2+Grade3+Grade4) and print the result in the picture box...

when user press ,the program calculates the summation of the four grades (Grade1+Grade2+Grade3+Grade4) and print the result in the picture box (picSum)when the user press , the program calculates the average of the four grades by calculating the summation firstly, and then divide the summation by 4(Grade1+Grade2+Grade3+Grade4)/4Finally, the results have to be printed in the picture box (picAvg)if the user forget to enter a value of one or more grade , or if the user entered a non-numaric value like “a”, the program must consider these unexpected values as zeros for example: if the user enter the values Grade1=8Grade2=9Grad3= “” (nothing: forget to enter a value)Grade4=”Ab”The summation must be 8+9+0 (instead of “”) + 0 (Instead of “AB”) =17if the user press button , the program must erase any value in the four Text Boxes ( txtGrade1 , txtGrade2, txtGrade3, txtGrade4), and the two picture boxes: picSum, and picAvg