Choose true$/$false and explain

$1.$ Accounts receivable confirmations must be controlled by the client from the time they are prepared until the time they are returned to the auditor.

$2.$ If a sale was for a valid shipment, but the amount of the sales invoice was calculated incorrectly, the accuracy objective was violated.

$3.$ Because auditors are responsible for having appropriate competence and capabilities to perform an audit, auditors are not normally permitted to consult with outside specialists during an audit engagement.

$4.$ Performance materiality impacts inherent risk and control risk.

$5.$ For a private company client, auditors are required to test any internal controls they believe have not been operating effectively during the period under audit.

$6.$ Acceptable audit risk and the amount of substantive evidence required are inversely related.