Final answer:
The style of letter described is known as Modified Block style, where only certain parts of the letter are centered.
Step-by-step explanation:
The style of letter that features the date line, the complimentary closing, and the typed signature line starting at the center of the page, with all other lines left justified, is called the Modified Block style. In contrast, the standard block formatting for business letters dictates that all elements should be left-justified and no lines should begin at the center. A font like size 12 Times New Roman or Arial is often used for readability, and the body of the letter should be single-spaced with a double space between paragraphs. For the closing, only the first word should be capitalized,followed by a comma, and the writer's name should be typed below after leaving two blank lines for the signature.