Before revision:  However, we further show that the corresponding objective is nondecreasing and satisfies submodularity . Therefore, a standard greedy algorithm offers an approximation factor of (1-1/e) at solving the problem.
After revision:  However, we further show that the corresponding objective is nondecreasing and satisfies submodularity and this allows a standard greedy algorithm offers an approximation factor of (1-1/e) at solving the problem.