Boss tweed encourages his associates to work "like a well-oiled machine", thus providing his workers with

a. an analogy
b. a heuristic
c. an algorithm
d. functional fixedness ( not correct)

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west

snell's law

refractve index = sin incidence / sin refraction