A continuous function p on [0,4] satisfies:
• p is increasing on [0,2].
• p is decreasing on [2,4].
A right Riemann sum with 4 equal subintervals is used to approximate ∫04p(x)dx. Indicate whether this approximation is necessarily an overestimate, necessarily an underestimate, or whether the sign of the error cannot be determined from the given information.