Multiply 5.9 by 10
An important spectral emission line has a wavelength of 21 cm. The corresponding photon energy is (h=6.62×10−34Js; c=3×108m/s)
Multiply:
(1) (−10) by (−15)
(2) (+35) by (−5)
(3) (−15) by (+8)
(4) (+10) by (−10)
(5) (+100) by (−10)