7) (a) Calculate the total muscle force vector from the following three quadriceps muscles: i) rectus femoris pulling 75 N at 5 laterally from the vertical, ii) vastus lateralis pulling 50 N at 30 laterally from the vertical, and iii) vastus medialis pulling 45 N at 40 medially from the vertical. (b) What is the fourth muscle that makes up the quadriceps muscle?