Planck's constant, h, is 6.626 x 10-34 js. the speed of light in a vacuum, c, is 3.00 x 108 m/s. calculate the frequency of a green laser with a wavelength of 510 nm

Can someone explain to me how to do this problem ?

Oxygen and nutrients are moved through the body by the: a. circulatory system c. lymphatic system b. digestive system d. reproductive system

The force acting on a beam was measured under the same operating conditions and a sample of 5 data points was collected. this process was repeated by 3 observers. the pooled standard deviations of these 3 data sets was 1.21. determine the true mean force using all pooled data (with a 95% probability). the result should look like this: true mean = mean +/- margin of error