4. The beginning of a for loop often starts with for i=1:length(x). a. What does the i represent? Could we name the i something different? b. In the loop, a variable is defined as springforce = k*x(i); but after the for loop runs, only one value is spit out, rather than the spring force for all x. Why? c. Can another for loop be placed within this for loop? Create an example in which the values of k also change, and a new array of the spring force is calculated. The result for springforce should be a matrix; each column in the matrix should represent the springforce at a different k value and each row should represent the springforce at a different x value. d. Plot the springforce as a function of x. Plot a different line for the springforce for each value of k and use different line types and a legend to differentiate.