Shadow length L can be written as:
2/x = L/12
where x is the distance the woman is from the spotlight.
So:
L = 24/x
dL/dx = -24/x^2
When she is 6m from the BUILDING, she's 18m from the light,
and:
dL/dx = -24/(18^2)
dL/dt = dL/dx * dx/dt = -24/(18^2) * 1.2 m/s = -0.088 m/s
It's shrinking at 8.8 cm/sec.
