Question \#4: Variables in the Main Program a. (4 points) We want to use the 'vec4' class in our program. What would be the 'include' directive that we would put at the beginning of the program? b. (4 points) Assuming that the 'include' directive has been correctly written, now write the declaration of a variable named 'tangent' that is of type 'vec4'. c. (2 points) True or false: if we want to use 'vec4' in a shader we do not have to provide an include statement