练习：赋值和修改变量现在该你来使用变量了。这道练习的注释（以#开头的行）提供了创建和修改变量的说明。请在每条注释后面根据说明写一行代码。注意，这段代码使用了科学记数法来定义很大的数字。4.445e8等于4.445 * 10 ** 8，也就是444500000.0。#代码注释 - 中英对照单词表：water reservoir 水库；volume：体积；rainfall 降雨；cubic metre 立方米The current volume of a water reservoir (in cubic metres) 目前水库的蓄水量（单位：立方米） reservoir_volume = 4.445e8The amount of rainfall from a storm (in cubic metres) 一场暴雨的降雨量（单位：立方米） rainfall = 5e6decrease the rainfall variable by 10% to account for runoff 考虑到流失的水量，将降雨量这个变量降低10%add the rainfall variable to the reservoir_volume variable 将降雨量与蓄水量相加increase reservoir_volume by 5% to account for stormwater that flows into the reservoir in the days following the storm 暴雨后的一段时间内，雨水会不断流入水库，考虑这部分水量，需要将水库的蓄水量变量增加 5%decrease reservoir_volume by 5% to account for evaporation 考虑到雨水蒸发情况，将蓄水量变量减小5% subtract 2.5e5 cubic metres from reservoir_volume to account for water that's piped to arid regions. 水库里的水会用来浇灌干涸地区，所以需要将蓄水量减少 2.5e5 立方米print the new value of the reservoir_volume variable 打印蓄水量变量的最新值# The current volume of a water reservoir (in cubic metres)reservoir_volume = 4.445e8# The amount of rainfall from a storm (in cubic metres)rainfall = 5e6# decrease the rainfall variable by 10% to account for runoff(1)# add the rainfall variable to the reservoir_volume variable(2)# increase reservoir_volume by 5% to account for stormwater that flows# into the reservoir in the days following the storm(3)# decrease reservoir_volume by 5% to account for evaporation(4)# subtract 2.5e5 cubic metres from reservoir_volume to account for water# that's piped to arid regions.(5)# print the new value of the reservoir_volume variable(6)