Karika 30

युगपच्चतुष्टयस्य तु वृत्तिः क्रमशश्च तस्य निर्दिष्टा। दृष्टे तथाप्यदृष्टे त्रयस्य तत्पूर्विका वृत्तिः ॥३०॥

yugapaccatuṣṭayasya tu vr̥ttiḥ kramaśaśca tasya nirdiṣṭā। dr̥ṣṭē tathāpyadr̥ṣṭē trayasya tatpūrvikā vr̥ttiḥ ॥30॥

[युगपत् चतुष्टयस्य तु वृत्तिः क्रमशः च तस्य निर्दिष्टा। दृष्टे तथा अपी अदृष्टे त्रयस्य तत् पूर्विका वृत्तिः॥
yugapat = the functions are simultaneous; catuṣṭayasya = of the set of four (buddhi, ahankara, manas, and senses); tu = but; vr̥ttiḥ = volition / mental acts; kramaśaḥ = in order; ca = and; tasya = its; nirdiṣṭā। = directed by; dr̥ṣṭē = observes; tathā = so; apī = too; adr̥ṣṭē = not observed; trayasya = by the three; tat pūrvikā = preceded by those; vr̥ttiḥ = activities;]

The mental acts (vr̥ttiḥ) are produced by the simultaneous functioning of the four (intellect, ego, mind, and senses) directed by what are sensed and not sensed, influenced by the three qualities based on previous mental acts (vr̥ttiḥ).

Sensed + Not sensed + three qualities based on previous mental acts = current mental acts
Agents involved: intellect, ego, mind, and senses.