Cost survey; admissibility

a. Where a cost survey, pursuant to recognized statistical and cost accounting practices, has been made for the trading area in which the offense is committed, to establish the lowest "cost to the retailer" and the lowest "cost to the wholesaler", said cost survey shall be deemed competent evidence to be used in proving the cost to the person complained against, within the provisions of this act. b. Any defendant, or any witness, in any civil action brought under the provisions of this act, may be required to testify, and the books, records, invoices, and all other documents of any such defendant, may be brought into court and introduced as evidence, but no defendant, or any witness in any such civil action, shall be prosecuted or subjected to any penalty or forfeiture for or on account of any transaction, matter or thing concerning which he may testify or produce evidence, documentary or otherwise, and no testimony given or produced shall be received against him upon any criminal proceeding or investigation.