const yearlyElectricCosts = (...monthCosts) => parseFloat(monthCosts.reduce((a, b) => a + b, 0).toFixed(2));/*input data come from parameters with zero default value, so it can calculate for any data and can be tested with different test cases*/const yearlyElectricCosts = (m1 = 0, m2 = 0, m3 = 0, m4 = 0, m5 = 0, m6 = 0, m7 = 0, m8 = 0, m9 = 0, m10 = 0, m11 = 0, m12 = 0 ) => {/* Create an object with 12 keys and the input values*/const monthlyCosts = {januaryBill : m1,februaryBill : m2,marchBill : m3,aprilBill : m4,mayBill : m5,juneBill : m6,julyBill : m7,augustBill : m8,septemberBill : m9,octoberBill : m10,novemberBill : m11,decemberBill : m12}/*print the object*/console.log(monthlyCosts);// Decide on a variable name and sum all the monthly chargesconst totalCharges = Object.values(monthlyCosts).reduce((acc, curr) => acc + curr, 0);// Return the value of the variable by typing it in after the `return` keyword belowconsole.log(totalCharges.toFixed(2), typeof(totalCharges.toFixed(2)));/*toFixed converts the result to string, we have to convert it back to number*/return parseFloat(totalCharges.toFixed(2));}- const yearlyElectricCosts = (...monthCosts) => parseFloat(monthCosts.reduce((a, b) => a + b, 0).toFixed(2));