r = 2
K = 10
h = 3

d = K^2 - 4*K*h/r
y1 = ( K - sqrt(d) )/2
y2 = ( K + sqrt(d) )/2

#postscript("../../WriteUp/Graphics/Chapter2/chap_2_sect_5_prob_21_plot.eps", onefile=FALSE, horizontal=FALSE)

ys = seq( 0, 15, length.out=100 )
fs = r * ( 1 - ys / K ) * ys - h 

plot( ys, fs, type='l', col='black', xlab='a', ylab='' )
abline(h=0, col='black')
abline(v=c( y1, y2 ), col='green')
grid()

#dev.off()