[R] curve fitting

[Dmitry Gospodaryov]

I have the data:
for x: 2, 8, 14, 20, 26, 32, 38, 44, 50, 56, 62, 68, 74,
for y: 100, 99, 99, 98, 97, 94, 82, 66, 48, 38, 22, 10, 1.
y depends on x by equation: y = 100*exp(b*(1-exp(c*x))/c),
where b and c are coefficients. I need to find coefficients in this
equation for given data. How can I do that by means of R?
Thank you for advance. With regard, Dmitry.