Question 11: it is easy to create an ellipse using a loop of string and two thumbtacks. the string is first stretched over the thumbtacks which act as foci. the string is then pulled tight using the pencil which can then trace out the ellipse. assume that you wish to draw an ellipse with a semi-major axis of a = 20 cm and e = 0.5. using what you have learned earlier in this lab, what would be the appropriate distances for a) the separation of the thumbtacks and b) the length of the string? fully explain how you determine these values.