In this fourth Scrabble exercise, we will determine the score of a word. You will define scrabble_score_word(row, k, word) to return the score for playing word at position k in the row. We extend the notation for rows: a row is still represented as a list of squares, but now a square can be: (1) a letter, (2) the start square, represented by the digit 0, (3) an empty square, or empty double- or triple-letter score square, represented by the integers 1, 2, 3, respectively, (4) an empty double- or triple-word square, represented by -2 or -3, respectively. To compute the score, you add up all the points for the letters first (counting letters double or triple as appropriate), then you multiply by any double or triple word scores (there might be several of these). Finally, if all seven letters were used, add a 35 point bonus. The scores for each letter are as follows: A=1, B=4, C=4, D=2, E=1, F=4, G=3, H=3, I=1, J=10, K=5, L=2, M=4, N=2, O=1, P=4, Q=10, R=1, S=1, T=1, U=2, V=5, W=4, X=8, Y=3, Z=10.