Some distant star is to be observed by some telescope of diameter of objective lens \( a \), at an angular resolution of \( 3.0 \times 10^{-7} \) radian. If the wavelength of light from the star reaching the telescope is \( 500 \, \text{nm} \), the minimum diameter of the objective lens of the telescope is ______ \( \text{cm} \). (Nearest integer)
