# Single first-order reaction
function foc(τ, (q, α, τ₋,  τ₊, k))
    exp(-k*τ)
end

# Competing first-order production and consumption reactions
function fopac(τ, kprod, kcons, substrate0, product0)
    (substrate0*kprod/(kcons - kprod))*(exp(-kprod*τ) - exp(-kcons*τ)) + product0*exp(-kcons*τ)
end
