At the hearing the board may adopt a resolution proposing modifications relating to any or all of the following: (a)a modification of the boundaries of the proposed improvement district, (b)the addition to the proposed improvement district of lands which in its opinion will be benefited by carrying out the purpose described in the resolution of intention, (c)the exclusion from the proposed improvement district of any lands described in the resolution of intention which in its opinion will not be benefited by carrying out such purpose or (d)the increasing, decreasing or otherwise modifying of the purpose stated in the resolution of intention. The resolution proposing modification shall describe the proposed modifications, state the change, if any, in the estimated expense of carrying out the purpose, and shall fix a time and place for hearing by the board thereon.