Determine the cost of water per thousand gallons of water (from local water board or a water bill). Calculate the cost of the drip per year from the information you have.
Determine the amount and cost of the water you use in taking your shower regularly. You will need to set the shower faucet as you normally do; record the time in minutes it takes you to shower; determine the amount of water used (by catching it and measuring it somehow) in one minute; and then calculate the savings per year using the procedure outlined above for the dripping faucet.
Lastly you are to measure the amount of water used by taking your regular shower and comparing it with the amount of water consumed in taking a "military shower" (alternately turn the water off and on to save as much water as you can).
Calculate the cost of water for one year to take your regular shower versus a military shower.