k = 1.2 (slider from 0 to 5, step 0.1)
k' = 0.7 (slider from 0 to 5, step 0.1)
f(x) = exp((k * x))
g(x) = exp(((-k) * x))
h(x) = exp((k' * x))
l(x) = exp(((-k') * x))