convert questions

`String.prototype.toUpperCase` returns a new string with all characters converted to uppercase. 

const str = 'hello';
const upper = str.toUpperCase();
console.log(upper); // 'HELLO'

`String.prototype.toLowerCase` returns a new string with all characters converted to lowercase. 

const str = 'HELLO';
const lower = str.toLowerCase();
console.log(lower); // 'hello'

The VALUE function converts text that represents a number into a numeric value. For example, =VALUE('1234') converts the text '1234' into the number 1234. This function is useful when working with text values that need to be used in numerical calculations.