[填空题]
A neutron star consists of neutrons at approximately nucl b8girbv*7w(jr m.)tmear density. Estimdxkri 3ar 66e6ate, fod6 re 3xrk6ai6r a 10-km-diameter neutron star,
(a) its mass number, A = $ \times 10^{55}$
(b) its mass (kg),m = $ \times 10^{29}\ \text{kg}$
(c) the acceleration of gravity at its surface. g = $ \times 10^{11}\ \text{m/s}^2$