A biologist is studying a population of beetles whose growth rate follows a cubic function \( f(x) = ax^3 + bx^2 + cx + d \). Observations show \( f(1) = 4 \), \( f(2) = 15 \), \( f(3) = 40 \), and \( f(4) = 85 \). Determine the coefficients \( a \), \( b \), \( c \), and \( d \). - Abu Waleed Tea