Answer:
a) Â f = 17,898 cm , b) Â P = 5.58D
Explanation:
a) For this exercise we must use the constructor equation
    1 / f = 1 / p + 1 / q
where f is the focal length and p, q are the distance to the object and the image, respectively
in this case they tell us that the distance to the point of near vision is q = 70.4 cm, here the image must be so that the person can see it normally
    1 / f = 1 / 24.0 + 1 / 70.4
    1 / f = 0.05587
    f = 17,898 cm
b) the power of a lens is defined as the inverse of the focal length in meters
     P = 1 / d
     p = 1 / 0.17898
     P = 5.58D